Mass-imbalanced ionic Hubbard chain

Article

关键词: FALICOV-KIMBALL MODEL;    MOTT INSULATOR;    ELECTRON CORRELATION;    SCALING BEHAVIOR;    PHASE-TRANSITION;    BAND INSULATOR;    ENERGY;    ATOMS;    STATE;    GAP;   

DOI  :  10.1103/PhysRevB.96.035116

来源: SCIE

【 摘 要 】

A repulsive Hubbard model with both spin-asymmetric hopping (t(up arrow) not equal t(down arrow)) and a staggered potential (of strength Delta) is studied in one dimension. The model is a compound of the mass-imbalanced (t(up arrow) not equal t(down arrow), Delta = 0) and ionic (t(up arrow) = t(down arrow), Delta > 0) Hubbard models, and may be realized by cold atoms in engineered optical lattices. We use mostly mean-field theory to determine the phases and phase transitions in the ground state for a half-filled band (one particle per site). We find that a period-two modulation of the particle (or charge) density and an alternating spin density coexist for arbitrary Hubbard interaction strength, U >= 0. The amplitude of the charge modulation is largest at U = 0, decreases with increasing U and tends to zero for U -> infinity. The amplitude for spin alternation increases with U and tends to saturation for U -> infinity. Charge order dominates below a value U-c, whereas magnetic order dominates above. The mean-field Hamiltonian has two gap parameters, Delta(up arrow) and Delta(down arrow), which have to be determined self-consistently. For U < U-c both parameters are positive, for U > U-c they have different signs, and for U > U-c one gap parameter jumps from a positive to a negative value. The weakly first-order phase transition at U-c can be interpreted in terms of an avoided criticality (or metallicity). The system is reluctant to restore a symmetry that has been broken explicitly.

【 授权许可】

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